Apparatus and method of ignition for combustible gases

ABSTRACT

A method and apparatus is described for igniting combustible gases by the zone heating of a pressure resistant, electrically conductive material with spaced apart electrical contacts on a surface of the material opposite the gases. After the ignition of the gases, the heated zone cools or is cooled and additional combustible gases can then be reintroduced for ignition by the same method. The material is preferably in the form of a small diameter metal tube with a portion of its length being electrically heated. The apparatus and method are particularly useful in the deburring of articles by controlling the ignition of the explosive gases in a rapidly and repetitively opened and sealed chamber for deburring articles by causing ignition of the gases in the sealed chamber at only that operator-selected portion of the cycle after maximum desired unexploded gas charge pressure has been obtained.

United States Patent Rice [5 APPARATUS AND METHOD OF IGNITION FORCOMBUSTIBLE GASES [75] Inventor: Warren A. Rice, Dexter, Mich.

173] Assignee: Chemotronics International. Inc.,

Ann Arbor, Mich.

[221 Filed: Aug. 17, 1973 [21] Appl. No: 389,251

[52] US. Cl 431/6; 123/169 C; 431/258; 317/82; 317/98 [51] Int. Cl. F23N5/20; F23N 5/22 [58] Field of Search 431/6. 263. 258; 317/82. 317/98;165/47; 123/169 C [56] References Cited UNITED STATES PATENTS 2.017.36410/1935 Anderson 123/169 c 2.273.651 2/1942 Lude 123/169 C 2.526.16910/1950 Steeg 431/263 X 3.071.182 1/1963 Delano... 431/6 3.191.6596/1965 Weiss 431/258 X 3.245.457 4/1966 Smith et al.... 431/6 3.662.2225/1972 Ray 317/98 FOREIGN PATENTS OR APPLICATIONS 571.170 5/1924 France123/169 C PROV/DING A COMBUS TIBLE STEP 64$ ADJACENT 44/ 54 5c TIP/(Al 4Y CONDUCT/4 E (OOL/A/G. #547250 zen/5 /4 w/n/ #547 TRANSFER Fay/04464/16 /5 70 cooL MATER/AL /0 STEP 3 561.991 5/1957 Italy 431/258Primary Eraminer-Charles J. Myhre Assistant Examiner-William C. AndersonAttorney, Agent, or FirnzMiller. Morriss. Pappas & McLeod 1 1 ABSTRACT Amethod and apparatus is described for igniting combustible gases by thezone heating of a pressure resistant. electrically conductive materialwith spaced apart electrical contacts on a surface of the materialopposite the gases. After the ignition of the gases. the heated zonecools or is cooled and additional combustible gases can then bereintroduced for ignition by the same method. The material is preferablyin the form of a small diameter metal tube with a portion of its lengthbeing electrically heated. The apparatus and method are particularlyuseful in the dcburring of articles by controlling the ignition of theexplosive gases in a rapidly and repetitively opened and sealed chamberfor deburring articles by causing ignition of the gases in the sealedchamber at only that operatorselected portion of the cycle after maximumdesired unexploded gas charge pressure has been obtained.

11 Claims, 4 Drawing Figures US. Patent N0v.11, 1 975 sheet'zofz3,918,878

APPARATUS AND METHOD OF IGNITION ,FOR

COMBUSTIBLE GASES SUMMARY OF INVENTION The present invention relates toan electrical apparatus for igniting combustible gases. In particular,the present invention relates to an apparatus with means whichelectrically heat a zone of a pressure resistant, electricallyconductive material to a temperature adjacent to the gases sufficientfor ignition. The pressure resistant material is preferably in the formof a metal tubeconnected with a sealed chamber such that the combustiblegases inside the chamber can be ignited from inside the tube.

PRIOR ART U. S. Pat. Nos. 3,475,229 and 3,666,252 show a method andvarious apparatus for thermally deburring articles by igniting acombustible gas in a sealed chamber. The chamber in the preferredequipment is opened for article removal and recycled rapidly on acontinuous basis. Such chambers can have preignition combustible gascharge pressures of up to 2,000 pounds per square inch (141 kilogram persquare centimeter) or more and generate large internally confinedexplosion pressures which can be on the order of 55 times the initialpreignition charge pressure. Such conditions cause rapid deteriorationand destruction of conventional igniter devices such as spark or glowplugs since they are designed to operate under much less severe ignitionconditions.

The prior art has utilized heated tubes to ignite combustible gasesusually in the operation of Otto or Diesel engines. In these devices,the igniter means is externally heated such as with a flame orelectrically prior to the introduction of combustible gases to initiallyignite the combustible gas as it is introduced intothe chambers. Oncethe engine is running at a steady state the external heating source isremoved and the igniter is maintained in a heated state at or above thecombustible gas autoignition temperature by the repeated exposure to theperiodically igniting gases. The patents to Nash (US. Pat. No. 563,051)and Vierling (U.S. Pat. No. 2,996,056) are illustrative.

In these prior art heated tube devices,.provision to minimize externalcooling of the igniter was made since this would stop the periodicignition of the combustible gas. Further, in initiating thegascombustion in these devices, no attempt is made to selectively heat onlya zone of the igniter, since it would ultimately be completely heated bythe operation of the engine in any event. Thus, the priorart heated tubedevices are heatedto or above the combustible gas ignition temperatureprior to the introduction of the combustible gas to the igniter.

It is-therefore an object of the present invention to provide an igniterapparatus and method of ignition of combustible gases which allows foroperator-selected control of the ignition of the combustible gases.Further, it is an object .of the present invention to provide an igniterapparatus which can be rapidly cycled without concern about prematureignition of the combusti- *ble' gases. It-is further an object of thepresent invention to provide igniters which-will withstand severerepetitive gas explosion conditions without failure. These and otherobjects will become increasingly apparent to those skilled in the artfrom the following description and by reference to the followingdrawings.

IN THE DRAWINGS:

FIG. I is a schematic illustration of the steps in the method of thepresent invention particularly showing the external heating of a zone ofa material in contact with a combustible gas and also schematicallyshowing a form of external cooling of the material using cooling gas orother fluid exposure, which can be forced air or liquid or which can beaccomplished by other convective means. 7

FIG. II is a front cross sectional view of a thermal deburring chamberillustrating a tubular igniter apparatus connected to a current sourcewith spaced apart cooled electrically conductive electrodes defining aheating zone of the tube.

FIG. III is a front exploded perspective view of the preferred igniterapparatus of the present invention.

FIG. IV is a front view of the preferred assembled igniter apparatusillustrated in FIG. III.

GENERAL DESCRIPTION the leads such that a zone of the heatable ignitermaterial is heated to produce ignition on the combustible gas side ofthe material when the leads are supplied from a current source; and heattransfer means in thermal contact with the heated zone of the ignitermaterial for cooling the heated zone to below the ignition temperatureof the combustible gas after the thermal energy release and pressurerise in the combustible gas in the chamber occurs by removing the heat.The present invention also relates to the method of igniting acombustible gas to produce a rapid thermal energy release and pressurerise which comprises: providing an ignit- ,able gas adjacent to anelectrically conductive igniter material having sufficient mechanicalstrength when heated to withstand a rapid thermal energy release andpressure rise in a gas adjacent to the igniter material; heating theigniter material by passing an electric current through a zone definedby spaced apart electrically conductive low resistance leads connectedto a current source to ignite the combustible gas; and cooling theheated zone of the igniter material to below the ignition temperatureafter the combustible gas has ignited.

The igniter material of the present invention is conductive and is spotor zone heated electrically. This material can be in various forms butis preferably a tube. The igniter materials are preferably composed ofhigh mechanical strength, and corrosion resistant metals such as thenickel-chrome alloys. Inconel is a particularly useful material since itis able to repetitively withi stand the thermal cycling and thepressures generated by explosive gases when heated to the ignitiontemperathe American Society for Metals Handbook Vol. I (I961 i The gaseswhich can be ignited by the method and apparatus of the presentinvention are combustible mixtures of an oxidizable material and anoxidizer material. Typical oxidizable gases are hydrogen. lower alkanes,alkcncs and alkynes, such as those containing 1 to 4 carbon atoms,ammonia, hydrazine, hydrogen sulfide, carbon monoxide and various otherrapidly oxidizable compounds.

Oxidizer compounds which can be used include air, oxygen, the halogens,such as fluorine and chlorine, ozone and various perchlorates andnitrogen oxides. Particularly preferred are the compositions shown inUS. Pat. No. 3,475,229.

Referring to FIG. I, the steps in the method and ignitcr of the presentinvention are illustrated. In Step 1 an ignitable gas 11 is providedadjacent to an electrically conductive material 10. In Step 2, thematerial is contacted with electrically conductive leads l2 and 12aconnected to a current source 13. The leads l2 and 12a heat the material10 to the ignition temperature of the gas 11. The distance is preferablybetween about I and 30 millimeters between the leads l2 and 12a. In Step3, fluid means 15, such as air, is used to cool the material 10 to belowthe combustible gas 11 ignition temperature. The steps of the method canbe performed by a specifically designed replaceable separate assembly.

Referring to FIG. I], a confined space 19 is formed by mating tooling 20and chamber 21. A pressure responsive seal 22 is mounted on the tooling20 in contact with the lower lip 21a of the chamber 21. Conduit 23 withvalve means 24 are provided leading to the confined space 21 for gasinlet and outlet. The tooling 20 is mounted on ram means 25 for closureof the tooling 20 with the chamber 21. The confined space 19 is providedwith an ignition tube 26 mounted on the chamber 21 with the closed endextending from the chamber 21. The tube was about 300 millimeters long,3 millimeters inside diameter and 6 millimeters outside diameter. Twospaced apart cooled electrodes 27 and 28 are mounted on the tube 26.Cooling of the electrodes was provided by tubes 33 and 34 around theelectrodes 27 and 28. The electrodes 27 and 28 were spaced apart about10 millimeters. The first electrode 28 was about 100 millimeters fromthe chamber end of the tube 26.

The tube 26 can be mounted on the tooling 20 or on the conduit 23 (notshown). The electrodes 27 and 28 are connected to a current source 29.

In operation of the device of FIG. II, the ram 25' is pulled down and anarticle 31 with burrs 32 is mounted on the tooling 20. The ram 25 isthen moved upward so that the tooling 20 and seal 22 close the chamber21 on the lip 21a. The valve 24 is opened to allow combustible gas toenter the confined space 19 and to fill the tube 26 and then closed. Thecurrent source 29 is then activated to ignite the gas by heating thetube 26 between the spaced apart electrodes 27 and 28.

SPECIFIC DESCRIPTION The preferred apparatus of the present invention isillustrated in FIGS. III and IV. The apparatus is similar in operationto that shown in FIG. II but modified to provide improved operatinglife. A heating zone 40 on a tube 41 with a closed end 42 is defined bycopper bushings 43 and 43a, l9 millimeters in diameter,

mounted on the tube 4] by silver soldering. This mating of the bushings43 and 43a to thctubc 4l, prevents corrosion at that interface. Thebushings 43 and 43a are slightly oversize in inside diameter to permitsilver soldering. The heating zone was 13 millimeters long. The tube 4]inside and outside diameters were 3.2 and 6.4 millimeters respectively.The further assemblies on bushings 43 and 43a are identical and only oneset will be described. Clamped around bushing 43 are two opposing copperbus bars 44 and 45 secured together by bolts 46 and threaded retainingplate 58. The copper to copper contact of the bus bars 44 and 45 andbushing 43 and 43a prevents corrosion, which would result from usingdissimilar metals, and helps to uniformly distribute the current aroundand into the tube 41. The extended portions of the bus bars 44 and 45are provided with coiled cooling tubes 47 and 48 brazed to the bus bars44 and 45.

The ends of the bus bars 44 and 45 are provided with bolts 49 and 50 formounting electrically conductive leads 51 and 52. The closed end 42 ofthe tube 41 is provided with an insulating positioning bracket 53secured by bolts 54 and 57 to a portion of the chamber or other fixedpart of the equipment (not shown). The bracket 53 loosely surrounds thetube 41 to allow the tube 41 to elongate on heating without bending. Theopen end of the tube 41 is provided with a hexagonal fitting 55 withthreads 56.

In operation of the apparatus of FIGS. III and IV, fitted to a chamber,electrical leads 51 and 52 are connected to a current source (not shown)and water or other cooling fluid is supplied through the tubes 47 and 48to cool the bus bars 44 and 45. Current is supplied equally at theidentical potential through leads 51 and 52 through zone 40 from the busbars 44 and 45 and through bushings 43 to ring 43a from the currentsource (not shown). The zone 40 is thus heated to ignite the combustiblegas provided inside the tube 41.

It has been found that the device of FIGS. Ill and IV will functionreliably for long periods of time and many firings without cracking ofthe tube 41, particularly in the heating zone 40. The reason for this isthat there are relatively uniform mechanical and thermal stresses on theheated zone because of the construction and mounting of the apparatus.The electrical leads 51 and 52; cooling tubes 47 and 48 and other tube41 compo nents are arranged to minimize mechanical stress on the zone40. Other bus bar means and cooling means providing this result willoccur to those skilled in the art.

The heated tube is so designed and located so as to minimize the heatrise of the tube from the explosion in the chamber and is also designedto maximize the heat loss when the current is turned off after theexplosion. This is necessary because the tube must be below the ignitiontemperature of the gas mixture between the selected ignition periods.

I claim: I

l. The method of igniting a combustible gas to pro'- duce a rapidthermal energy release and pressure rise which comprises:

a. providing an ignitable gas adjacent to and on one side of anelectrically conductive igniter material having sufficient mechanicalstrength when heated to withstand a rapid thermal energy release andpressure rise in the gas adjacent to the igniter material and havingsufficient surface on the side opposite the gas to permit cooling;

b. heating the igniter material by passing an electric current throughthe material such that a zone between spaced apart electricallyconductive low resistance leads connected to a current source is heatedto ignite the combustible gas; and

c. cooling the heated zone of the igniter material using a heat transfermeans on the surface opposite the gas to below the ignition temperatureafter the combustible gas has ignited.

2. The method of claim 1 wherein the conductive leads are moved into andout of contact with the igniter material.

3. The method of claim 1 wherein the combustible gas is provided incontact with the igniter material inside a sealed chamber.

4. The method of claim 1 wherein heat transfer means is forced air incontact with the igniter material on the side opposite the gas side ofthe surface.

5. The igniter apparatus adapted to be fitted on a combustible gascontaining chamber to produce ignition of the gas with a consequentrapid thermal energy release and pressure rise which comprises:

a. an integral heatable electrically conductive igniter materialprovided with means adapted to be fitted to a gas ignition chamber andbeing of sufficient mechanical strength to be able to withstand a rapidthermal energy release and pressure rise in a gas on one side of thematerial and with a surface permit- 7 ting cooling heat transfer on theside opposite the combustible gas side of the material;

b. electrically conductive low resistance leads connected to the ignitermaterial to form a conductive path between the leads through thematerial such that a zone of the heatable igniter material between theleads is heated to produce ignition on the combustible gas side of thematerial when the leads are supplied from a current source; and

. heat transfer means mounted adjacent to the surface opposite thecombustible gas side of the material and in thermal contact with theheated zone of the igniter material for cooling the heated zone to belowthe ignition temperature of the combustible gas by removing the heatafter the thermal energy release and pressure rise in the combustiblegas in the chamber occurs.

6. The apparatus of claim 5 wherein the igniter material is in the formof a tube with sides extending from the means adapted to be fitted tothe chamber to a closed end and an open end at the end with the meansadapted to be fitted to the chamber and wherein the leads are connectedto the exterior sides of the tube opposite the gas combustion side ofthe igniter material to provide the heatable zones.

7. The apparatus of claim 5 wherein the heated zone of the ignitermaterial is adapted to fit inside the chamber. 1 I v g 8. The apparatusof claim 5 wherein the electrically conductive leads are provided withfluid cooling.

9. The apparatus of claim 5 wherein the heat transfer means is aircooled surfaces mounted adjacent the heated zone.

10. The apparatus of claim 9 wherein the air cooled surfaces areelectrically conductive and the leads are connected to the ignitionmeans surface through the cooled surfaces.

11. The apparatus of claim 5 wherein a current source is connected tothe leads and wherein the igniter material is fitted to the chamber.

1. THE METHOD OF IGNITING A COMBUSTIBLE GAS TO PRODUCE A RAPID THERMALENERGY RELEASE AND PRESSURE RISE WHICH COMPRISES: A. PROVIDING ANIGNITABLE GAS ADJACENT TO AND ON ONE SIDE OF AN ELECTRICALLY CONDUCTIVEINGNITER MATERIAL HAVING SUFFICIENT MECHINICAL STRENGTH WHEN HEATED TOWITHSTAND A RAPID TERMAL ENERGY RELEASE AND PRESSURE RISE IN THE GASADJACENT TO THE IGNITER MATERIAL AND HAVING SUFFICIENT SURFACE ON THESIDE OPPOSITE THE GAS TO PERMIT COOLING: B. HEATING THE IGNITER MATERIALBY PASSING AN ELECTRIC CURRENT THROUGH THE MATERIAL SUCH THAT A ZONEBETWEEN SPACED APART ELECTRICALLY CONDUCTIVE LOW RESISTANCE LEADS CON-2. The method of claim 1 wherein the conductive leads are moved into andout of contact with the igniter material.
 3. The method of claim 1wherein the combustible gas is provided in contact with the ignitermaterial inside a sealed chamber.
 4. The method of claim 1 wherein heattransfer means is forced air in contact with the igniter material on theside opposite the gas side of the surface.
 5. The igniter apparatusadapted to be fitted on a combustible gas containing chamber to produceignition of the gas with a consequent rapid thermal energy release andpressure rise which comprises: a. an integral heatable electricallyconductive igniter material provided with means adapted to be fitted toa gas ignition chamber and being of sufficient mechanical strength to beable to withstand a rapid thermal energy release and pressure rise in agas on one side of the material and with a surface permitting coolingheat transfer on the side opposite the combustible gas side of thematerial; b. electrically conductive low resistance leads connected tothe igniter material to form a conductive path between the leads throughthe material such that a zone of the heatable igniter material betweenthe leads is heated to produce ignition on the combustible gas side ofthe material when the leads are supplied from a current source; and c.heat transfer means mounted adjacent to the surface opposite thecombustible gas side of the material and in thermal contact with theheated zone of the igniter material for cooling the heated zone to belowthe ignition temperature of the combustible gas by removing the heatafter the thermal energy release and pressure rise in the combustiblegas in the chamber occurs.
 6. The apparatus of claim 5 wherein theigniter material is in the form of a tube with sides extending from themeans adapted to be fitted to the chamber to a closed end and an openend at the end with the means adapted to be fitted to the chamber andwherein the leads are connected to the exterior sides of the tubeopposite the gas combustion side of the igniter material to provide theheatable zones.
 7. The apparatus of claim 5 wherein the heated zone ofthe igniter material is adapted to fit inside the chamber.
 8. Theapparatus of claim 5 wherein the electrically conductive leads areprovided with fluid cooling.
 9. The apparatus of claim 5 wherein theheat transfer means is air cooled surfaces mounted adjacent the heatedzone.
 10. The apparatus of claim 9 wherein the air cooled surfaces areelectrically conductive and the leads are connected to the ignitionmeans surface through the cooled surfaces.
 11. The apparatus of claim 5wherein a current source is connected to the leads and wherein theigniter material is fitted to the chamber.